# The leaderboard payload as published by Api::V1::LeaderboardController.
#
# The API serves this out of a short cache, so what a consumer of the endpoint
# sees is whatever landed in `CACHE_KEY` on the last refresh -- not a live read
# of the players table. The admin screen reads that same cached entry, which is
# why the key, the TTL and the shape all live here rather than in the
# controller: one place publishes, both places agree on what "published" means.
class LeaderboardPayload
  CACHE_KEY = "api/v1/leaderboard".freeze
  TTL       = 1.minute

  # What the API returns. Recomputes and republishes when the cache is cold.
  def self.fetch
    Rails.cache.fetch(CACHE_KEY, expires_in: TTL) do
      DemoActivity.simulate! # TEMP: fake gameplay so the banner has moving numbers
      build
    end
  end


  # The currently published payload, or nil when the cache has expired and no
  # one has called the endpoint since. Never computes, never publishes -- the
  # admin screen uses this to show what consumers are actually being served.
  def self.published
    Rails.cache.read(CACHE_KEY)
  end


  # A fresh payload that is NOT written to the cache and does not invent demo
  # players. This is what the next API call would publish.
  def self.build
    leaderboard = LeaderboardScore.call

    {
      leaderboard: leaderboard,
      badges:      LeaderboardBadges.call(leaderboard),
      updated_at:  Time.current
    }
  end


  def self.expire!
    Rails.cache.delete(CACHE_KEY)
  end
end